When changing the status of an open Opportunity to 'Closed-Won' or "Closed-Lost', you receive the error "Object reference is not set to instance of an object."
Family: Sage ACT!
Product: Sage ACT! Pro, Sage ACT! Premium
This issue is currently under investigation. This will occur if the Probability field is removed from the Opportunity layout you are currently using.
To resolve this issue, you will need to add the Probability field back to your Opportunity layout or switch to a layout that includes this field.
Designing Layouts in Sage ACT!
Answer ID: Designing Layouts in Act!